Electrode contact with hydrogel covering

A cochlear implant electrode comprising:

• an implantable electrode array made of resilient material having a center longitudinal axis and an outer surface;
• a plurality of electrode contacts distributed on the outer surface of the electrode array along the longitudinal axis for applying electrical stimulation signals to adjacent neural tissue;
• and
• at least one biocompatible hydrogel layer fixed to the electrode array solely by mechanical connection and adapted to swell from contact with perilymph fluid within a cochlea without separating away from the outer surface of the electrode array;
• wherein the electrode array includes at least two openings connected together through the interior of the electrode array and filled with hydrogel material of the hydrogel layer to form a closed loop of hydrogel material to mechanically connect the hydrogel layer to the electrode array.